The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Dario Farina - One of the best experts on this subject based on the ideXlab platform.
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decoding motor neuron activity from epimysial thin film electrode recordings following targeted muscle reinnervation
Journal of Neural Engineering, 2019Co-Authors: Silvia Muceli, Kd Bergmeister, Oc Aszmann, Klauspeter Hoffmann, Martin Aman, Ivan Vukajlija, Dario FarinaAbstract:Objective Surface electromyography (EMG) is currently used as a control signal for active prostheses in amputees who underwent targeted muscle reinnervation (TMR) surgery. Recent research has shown that it is possible to access the spiking activity of spinal motor neurons from multi-channel surface EMG. In this study, we propose the use of multi-channel epimysial EMG electrodes as an interface for decoding motor neurons activity following TMR. Approach We tested multi-channel epimysial electrodes (48 detection sites) built with thin-film technology in an animal model of TMR. Eight animals were tested 12 weeks after reinnervation of the biceps brachii lateral head by the ulnar nerve. We identified the position of the innervation zone and the muscle fiber conduction velocity of motor units decoded from the multi-channel epimysial recordings. Moreover, we characterized the pick-up volume by the distribution of the motor unit Action Potential Amplitude over the epimysium surface. Main results The electrodes provided high quality signals with average signal-to-noise ratio >30 dB across 95 identified motor units. The motor unit Action Potential Amplitude decreased with increasing distance of the electrode from the muscle fibers (P [Formula: see text] 0.001). The decrease was more pronounced for bipolar compared to monopolar derivations. The average muscle fiber conduction velocity was 2.46 ± 0.83 m s-1. Most of the neuromuscular junctions were close to the region where the nerve was neurotized, as observed from the EMG recordings and imaging data. Significance These results show that epimysial electrodes can be used for selective recordings of motor unit activities with a pick-up volume that included the entire muscle in the rat hindlimb. Epimysial electrodes can thus be used for detecting motor unit activity in muscles with specific fascicular territories associated to different functions following TMR surgery.
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Cancellation of surface Action Potential Amplitude in motor units of the vastus medialis muscle
Neuroscience, 2007Co-Authors: Corrado Cescon, Francesco Negro, Roger M. Enoka, Dario FarinaAbstract:The surface EMG underestimates the amount of motor unit activity due to the loss of information that occurs when positive and negative phases of Action Potentials cancel one another and reduce the Amplitude of the signal (cancellation) It has been shown in simulation [1] that cancellation of Action Potentials of individual motor units is linearly correlated to the decrease in size of the spike-triggered average of the rectified or squared EMG Thus, spike-triggered averaging [2,3] of the surface EMG can be in principle used to estimate Amplitude cancellation but this has not been supported theoretically or verified experimentally Theoretical analysis of cancellation of single motor unit Action Potentials in relation to spike-triggered averaging to explain the results reported previously in simulation [1] Validation of the theoretical predictions with experimental recordings of motor units in the vastus medialis muscle The amount of cancellation of Action Potentials of individual motor units has been theoretically proven to depend only on the ratio between the RMS of the motor unit Action Potential and the RMS of the interference signal. According to this theoretical derivation, small surface Action Potentials are cancelled more than large Action Potentials. The ratio between the spike-triggered average of the interference and the squared surface EMG is theoretically equivalent to the degree of cancellation of the Action Potential, which explains the results reported in [1]. The theoretical predictions have been experimentally validated for the vastus medialis muscle. Cancellation of Action Potential Amplitude of single motor units can thus be theoretically predicted and experimentally quantified.
Tatsushi Toda - One of the best experts on this subject based on the ideXlab platform.
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ultrasonographic diaphragm thickness correlates with compound muscle Action Potential Amplitude and forced vital capacity
Muscle & Nerve, 2016Co-Authors: Yoshikatsu Noda, Kenji Sekiguchi, Nobuo Kohara, Fumio Kanda, Tatsushi TodaAbstract:Introduction: Noninvasive evaluation of respiratory function in patients with various neuromuscular disorders is important for predicting life expectancy. Methods: We performed B-mode ultrasonography (USG) and nerve conduction studies in 37 patients (16 had amyotrophic lateral sclerosis; 11, myopathy; and 10, neuropathy) and 10 controls. USG of the diaphragm was performed in the supine position using a linear probe over the intercostal space at the anterior axillary line. Diaphragm muscle thickness was measured at end-expiration. The Amplitude of diaphragm compound muscle Action Potentials (CMAP) was obtained by phrenic nerve stimulation with a surface electrode. Respiratory function was measured with standard pulmonary function tests including forced vital capacity (FVC). Results: Diaphragm thickness was significantly correlated with FVC (r = 0.74) and CMAP Amplitude (r = 0.53). Conclusions: Diaphragm USG is useful for objective evaluation of pulmonary function in neuromuscular disorders without requiring undue patient effort or cooperation. Muscle Nerve, 2015
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ultrasonographic diaphragm thickness correlates with compound muscle Action Potential Amplitude and forced vital capacity
Muscle & Nerve, 2016Co-Authors: Yoshikatsu Noda, Kenji Sekiguchi, Nobuo Kohara, Fumio Kanda, Tatsushi TodaAbstract:Introduction Noninvasive evaluation of respiratory function in patients with various neuromuscular disorders is important for predicting life expectancy. Methods We performed B-mode ultrasonography (USG) and nerve conduction studies in 37 patients (16 had amyotrophic lateral sclerosis; 11, myopathy; and 10, neuropathy) and 10 controls. USG of the diaphragm was performed in the supine position using a linear probe over the intercostal space at the anterior axillary line. Diaphragm muscle thickness was measured at end-expiration. The Amplitude of diaphragm compound muscle Action Potentials (CMAP) was obtained by phrenic nerve stimulation with a surface electrode. Respiratory function was measured with standard pulmonary function tests including forced vital capacity (FVC). Results Diaphragm thickness was significantly correlated with FVC (r = 0.74) and CMAP Amplitude (r = 0.53). Conclusions Diaphragm USG is useful for objective evaluation of pulmonary function in neuromuscular disorders without requiring undue patient effort or cooperation.
Bryan E Pfingst - One of the best experts on this subject based on the ideXlab platform.
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a broadly applicable method for characterizing the slope of the electrically evoked compound Action Potential Amplitude growth function
Ear and Hearing, 2021Co-Authors: Jeffrey Skidmore, Dyan Ramekers, Deborah J Colesa, Kara C Schvartzleyzac, Bryan E PfingstAbstract:Objectives Amplitudes of electrically evoked compound Action Potentials (eCAPs) as a function of the stimulation level constitute the eCAP Amplitude growth function (AGF). The slope of the eCAP AGF (i.e., rate of growth of eCAP Amplitude as a function of stimulation level), recorded from subjects with cochlear implants (CIs), has been widely used as an indicator of survival of cochlear nerve fibers. However, substantial variation in the approach used to calculate the slope of the eCAP AGF makes it difficult to compare results across studies. In this study, we developed an improved slope-fitting method by addressing the limitations of previously used approaches and ensuring its application for the estimation of the maximum slopes of the eCAP AGFs recorded in both animal models and human listeners with various etiologies. Design The new eCAP AGF fitting method was designed based on sliding window linear regression. Slopes of the eCAP AGF estimated using this new fitting method were calculated and compared with those estimated using four other fitting methods reported in the literature. These four methods were nonlinear regression with a sigmoid function, linear regression, gradient calculation, and boxcar smoothing. The comparison was based on the fitting results of 72 eCAP AGFs recorded from 18 acutely implanted guinea pigs, 46 eCAP AGFs recorded from 23 chronically implanted guinea pigs, and 2094 eCAP AGFs recorded from 200 human CI users from 4 patient populations. The effect of the choice of input units of the eCAP AGF (linear versus logarithmic) on fitting results was also evaluated. Results The slope of the eCAP AGF was significantly influenced by the slope-fitting method and by the choice of input units. Overall, slopes estimated using all five fitting methods reflected known patterns of neural survival in human patient populations and were significantly correlated with speech perception scores. However, slopes estimated using the newly developed method showed the highest correlation with spiral ganglion neuron density among all five fitting methods for animal models. In addition, this new method could reliably and accurately estimate the slope for 4 human patient populations, while the performance of the other methods was highly influenced by the morphology of the eCAP AGF. Conclusions The novel slope-fitting method presented in this study addressed the limitations of the other methods reported in the literature and successfully characterized the slope of the eCAP AGF for various animal models and CI patient populations. This method may be useful for researchers in conducting scientific studies and for clinicians in providing clinical care for CI users.
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across site patterns of electrically evoked compound Action Potential Amplitude growth functions in multichannel cochlear implant recipients and the effects of the interphase gap
Hearing Research, 2016Co-Authors: Kara C Schvartzleyzac, Bryan E PfingstAbstract:Electrically evoked compound Action Potential (ECAP) measures of peak Amplitude, and Amplitude-growth function (AGF) slope have been shown to reflect characteristics of cochlear health (primarily spiral ganglion density) in anesthetized cochlear-implanted guinea pigs. Likewise, the effect of increasing the interphase gap (IPG) in each of these measures also reflects SGN density in the implanted guinea pig. Based on these findings, we hypothesize that suprathreshold ECAP measures, and also how they change as the IPG is increased, have the Potential to be clinically applicable in human subjects. However, further work is first needed in order to determine the characteristics of these measures in humans who use cochlear implants. The current study examined across-site patterns of suprathreshold ECAP measures in 10 bilaterally-implanted, adult cochlear implant users. Results showed that both peak Amplitude and slope of the AGF varied significantly from electrode to electrode in ear-specific patterns across the subjects' electrode arrays. As expected, increasing the IPG on average increased the peak Amplitude and slope. Across ears, there was a significant, negative correlation between the slope of the ECAP AGF and the duration of hearing loss. Across-site patterns of ECAP peak Amplitude and AGF slopes were also compared with common ground impedance values and significant correlations were observed in some cases, depending on the subject and condition. The results of this study, coupled with previous studies in animals, suggest that it is feasible to measure the change in suprathreshold ECAP measures as the IPG increases on most electrodes. Further work is needed to investigate the relationship between these measures and cochlear implant outcomes, and determine how these measures might be used when programming a cochlear-implant processor.
Hatice Tankisi - One of the best experts on this subject based on the ideXlab platform.
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motor unit number index and compound muscle Action Potential Amplitude
Clinical Neurophysiology, 2019Co-Authors: H Bostock, A B Jacobsen, Hatice TankisiAbstract:Abstract Objectives MUNIX (motor unit number index), derived from the compound muscle Action Potential (CMAP) and surface EMG interference pattern (SIP) has become popular as a substitute for motor unit number estimation (MUNE). This study was undertaken to determine why, in recent recordings from amyotrophic lateral sclerosis (ALS) patients and healthy controls, we found that MUNIX values resembled CMAP Amplitudes more closely than MUNE values. Methods The relationship between MUNIX and CMAP and SIP Amplitudes was investigated by a theoretical analysis and by reanalysing the data from the previous study. Results Theory indicates that when motor unit Potentials overlap extensively, information about motor unit size and number is lost, and MUNIX depends only on CMAP area and power. Accordingly, MUNIX values were found to be sensitive to changes in CMAP Amplitude but insensitive to changes in SIP Amplitude. The reproducibility of MUNIX measurements in healthy controls was found to depend almost entirely on correlation with CMAP properties. Conclusions MUNIX gives misleading information about motor unit numbers in healthy controls, and provides little information about loss of motor units in ALS patients beyond that given by simple CMAP Amplitude measurements. Significance MUNIX should not be interpreted as a MUNE method.
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correlation between compound muscle Action Potential Amplitude and duration in axonal and demyelinating polyneuropathy
Clinical Neurophysiology, 2012Co-Authors: Hatice Tankisi, Marit Otto, Kirsten Pugdahl, Birger Johnsen, Anders FuglsangfrederiksenAbstract:Abstract Objective To get a better understanding of pathophysiology in polyneuropathies (PNPs) by correlating compound muscle Action Potential (CMAP) Amplitude with duration. Methods A total of 145 motor nerve conduction studies (MNCS) in 53 axonal and 132 MNCS in 45 demyelinating PNPs were analyzed. Peroneal and tibial MNCS were done by surface stimulation while for median and ulnar nerves near nerve or surface stimulations were used. CMAP Amplitude and duration were compared in axonal and demyelination PNPs. Relationships between Amplitude and duration of distally and proximally evoked CMAP were examined using regression analysis. Results CMAP Amplitude was lower and duration was increased in all examined nerves in demyelinating PNPs than in axonal PNPs. In demyelinating PNPs, an inverse linear correlation between Amplitude and duration was seen in distally and proximally evoked CMAP in all examined nerves. In axonal PNPs, there was no correlation in any of the nerves neither in distally nor in proximally evoked CMAP. Conclusions Distal CMAP duration and the relationship between CMAP Amplitude and duration show supplementary electrodiagnostic Potential in demyelinating PNPs. Significance More knowledge about the relation between Amplitude and duration in axonal lesions and demyelination may help to reveal the pathophysiology in PNPs. Significant correlation between Amplitude and duration in demyelination may suggest that the severe decrease in Amplitude in demyelinating PNPs is probably due to the increase in duration secondary to temporal dispersion.
Yoshikatsu Noda - One of the best experts on this subject based on the ideXlab platform.
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ultrasonographic diaphragm thickness correlates with compound muscle Action Potential Amplitude and forced vital capacity
Muscle & Nerve, 2016Co-Authors: Yoshikatsu Noda, Kenji Sekiguchi, Nobuo Kohara, Fumio Kanda, Tatsushi TodaAbstract:Introduction: Noninvasive evaluation of respiratory function in patients with various neuromuscular disorders is important for predicting life expectancy. Methods: We performed B-mode ultrasonography (USG) and nerve conduction studies in 37 patients (16 had amyotrophic lateral sclerosis; 11, myopathy; and 10, neuropathy) and 10 controls. USG of the diaphragm was performed in the supine position using a linear probe over the intercostal space at the anterior axillary line. Diaphragm muscle thickness was measured at end-expiration. The Amplitude of diaphragm compound muscle Action Potentials (CMAP) was obtained by phrenic nerve stimulation with a surface electrode. Respiratory function was measured with standard pulmonary function tests including forced vital capacity (FVC). Results: Diaphragm thickness was significantly correlated with FVC (r = 0.74) and CMAP Amplitude (r = 0.53). Conclusions: Diaphragm USG is useful for objective evaluation of pulmonary function in neuromuscular disorders without requiring undue patient effort or cooperation. Muscle Nerve, 2015
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ultrasonographic diaphragm thickness correlates with compound muscle Action Potential Amplitude and forced vital capacity
Muscle & Nerve, 2016Co-Authors: Yoshikatsu Noda, Kenji Sekiguchi, Nobuo Kohara, Fumio Kanda, Tatsushi TodaAbstract:Introduction Noninvasive evaluation of respiratory function in patients with various neuromuscular disorders is important for predicting life expectancy. Methods We performed B-mode ultrasonography (USG) and nerve conduction studies in 37 patients (16 had amyotrophic lateral sclerosis; 11, myopathy; and 10, neuropathy) and 10 controls. USG of the diaphragm was performed in the supine position using a linear probe over the intercostal space at the anterior axillary line. Diaphragm muscle thickness was measured at end-expiration. The Amplitude of diaphragm compound muscle Action Potentials (CMAP) was obtained by phrenic nerve stimulation with a surface electrode. Respiratory function was measured with standard pulmonary function tests including forced vital capacity (FVC). Results Diaphragm thickness was significantly correlated with FVC (r = 0.74) and CMAP Amplitude (r = 0.53). Conclusions Diaphragm USG is useful for objective evaluation of pulmonary function in neuromuscular disorders without requiring undue patient effort or cooperation.
